1. Field of the Invention
The present invention relates to a method for forming a quantum well structure and a method for manufacturing a semiconductor light emitting element.
2. Description of the Related Art
In recent years, some type of group III nitride-based semiconductor light emitting element includes an active layer having a multiquantum well (MQW) structure in which well layers each composed of a group III nitride semiconductor which includes indium (hereinafter referred as “In” in some cases) and another group III element (such as gallium) and barrier layers each composed of GaN or InGaN which has a band gap wider than that of each well layer are alternately laminated to each other. In the MQW structure as described above, when the well layer is grown on the barrier layer, a starting material gas for In (such as trimethylindium), a starting material gas for the other group III element (such as trimethylgallium), and a starting material gas for N (such as ammonia) are simultaneously supplied to a growth furnace so as to epitaxially grow a group III nitride semiconductor crystal.
As a related technique, in Japanese Unexamined Patent Application Publication No. 2001-192828, a pre-flow operation has been disclosed in which when a predetermined film is formed on a surface of a workpiece using a high melting point metal compound gas and a reducing gas, one of the high melting point metal compound gas and the reducing gas is supplied before the other gas is supplied. In addition, in “Effects of TMIn flow on the interface and optical properties of InGaN/GaN multiquantum wells”, by J. P. Liu et al., Journal of Crystal Growth, ELSEVIER, Volume 264, pp. 53 to 57 (2004), a technique has been disclosed in which a multiquantum well structure including InGaN well layers and GaN barrier layers is formed by a metal organic chemical vapor deposition (MOCVD) method on a GaN layer which has the (0001) plane as a growth surface and which is formed on a sapphire substrate. According to the this document, before an InGaN well layer is grown which has a photoluminescence (PL) wavelength in a blue-violet range in the vicinity of a wavelength of 405 nm, pre-flow of trimethylindium is performed for a predetermined time.